Geographically, the tropical atmosphere lies between the Tropic of Cancer and the Tropic of Capricorn. But from meteorological point of view, the boundaries of the tropical atmosphere are determined by the high pressure cells of the subtropics in both the hemispheres.
About half the area of the earth’s surface lies within the tropics where 40 per cent of the worlds total population lives. Therefore the climatologically study of the tropical atmosphere becomes all the more important.
It is rather interesting to point put that prior to World War II the tropical weather used to be considered as monotonous and uneventful.
But when during the war the military aeroplanes had to take flights in this atmosphere, the myth of the generally fair and uneventful weather of the low latitudes was exploded.
Paucity of weather observatories and lack of observational data were the main hurdles in obtaining a correct picture of tropical weather. That is why the weather scientists, particularly of the west, had a very simplified picture of tropical atmosphere.
Since 1960 a large number of weather satellites such as Tiros, Nimbus, Essu, Itos, Nova, etc. have been engaged in making a probe of the upper parts of the atmosphere. This has resulted in startling revelations about the tropical weather and climate.
These weather satellites have helped in understanding the various weather processes and weather systems of the tropical atmosphere. They have also increased our knowledge of the various atmospheric disturbances which largely control the weather within the tropics.
Now the evidences exist to prove that various kinds of weather disturbances exist within the tropics. A great deal of variability has been observed in weather elements like temperature, precipitation, pressure etc. However, there is no clear-cut distinction between different types of atmospheric disturbances that originate within the tropics.
Only the violent tropical storms like hurricanes and typhoons have been seriously studied by the climatologists. These severe storms are not only limited in number, but they are also restricted to limited areas.
But it is the weaker and milder forms of tropical disturbances which affect the weather to a considerable extent and break the so-called monotony of the tropical weather. Most of the extensive tropical disturbances are the weak and shallow low-pressure systems dominating the weather of the humid tropics.
When we compare the weather phenomena of the tropical region with those of the temperate, zone, significant differences emerge. The tropical region lacks rapid and violent changes in day- to-day weather as are so conspicuous in the middle latitudes.
No doubt, the tropical weather is generally unsettled. Even then the most characteristic feature of the tropical region is a depressing and monotonous hot weather.